1. Field of the Invention
The present invention relates to an optimum accommodation design method for a client signal using an optical transmission/reception card, and an optimum design method for an optical network.
2. Description of the Related Art
In recent years, an optical transmission/reception card (transponder card), generically called ADM on λ, ADM on a card, et cetera, integrally equipped with an Add/Drop function of a SONET signal (ANSI T1. 105 recommendation: Synchronous Optical Network Basic Description Including Multiplex Structures, Rates and Formats) and an SDH signal (ITU-T Recommendation G.803: Architecture of Transport Networks Based on the Synchronous Digital Hierarchy) and an optical signal transponder function (i.e., the function of generating a signal light) has been developed for enabling a construction of an upper layer network accommodating diverse client signals including a SONET signal, SDH signal (simply “SONET/SDH” hereinafter), Ethernet (registered trademark) and fiber channel on an optical network structured by a wavelength division multiplexing (WDM) system.
The focused here is a design technique for accommodating a client signal, which is accommodated by a SONET/SDH network built up on a WDM net, to a SONET/SDH frame.
FIG. 1 exemplifies a mapping of a SONET signal frame.
FIG. 1 exemplifies a mapping of four OC48s, which are SONET signals, to a SONET frame of OC192.
When multiplexing four OC48s and mapping in a SONET frame of the OC192, an overhead part of each frame of the OC48 is separated and it is mapped together with an overhead part of the OC192 frame. And each payload part of the OC48 is mapped together with that of the OC192.
FIG. 2 is a diagram describing a technique premised by the present invention.
Conventionally, a WDM network and a SONET/SDH network built thereon are constituted by respectively different apparatuses, namely a WDM apparatus and an SONET/SDH ADM (Add/Drop Multiplexing) apparatus. The WDM apparatus is one for carrying out a wavelength multiplexing by making optical signals carried on different wavelength lights, while the SONET/SDH ADM apparatus is one generating a signal carried on one wavelength light by applying a time division multiplexing to client signals of individual channels. A purpose of a design for accommodating a client signal on the network is to accommodate all the given client signals and minimize the number of SONET/SDH ADM apparatuses required for the accommodation, thereby minimizing an apparatus cost. In the case of accommodating client signals by using the SONET/SDH ADM apparatus, such accommodation has conventionally been carried out so as to raise bandwidth usage efficiency of each optical signal in consideration of a bandwidth of each client signal. The number of client signal ports of the SONET/SDH ADM apparatus is generally large, making it unnecessary to consider the number of client signals per optical signal, and therefore a combination gaining the maximum band usage ratio of optical signals independent of the number of client signals has been selected in priority. That is, the conventional accommodation design has made it possible to equip an interface for the worth of the number of ports capable of accommodating client signals of the worth of a natural number obtained by the following expression (1) for all client signals:
                              (                      The            ⁢                                                  ⁢            number            ⁢                                                  ⁢            of            ⁢                                                  ⁢            ports            ⁢                                                  ⁢            on            ⁢                                                                      ⁢                                                                    ⁢            the            ⁢                                                                      ⁢                                                                    ⁢            client            ⁢                                                  ⁢            signal            ⁢                                                  ⁢            side                    )                =                              (                          optical              ⁢                                                                                ⁢                                                                              ⁢              signal              ⁢                                                          ⁢              bandwidth              ⁢                                                          ⁢              of              ⁢                                                          ⁢              a              ⁢                                                          ⁢              SONET              ⁢                              /                            ⁢              SDH              ⁢                                                          ⁢              ADM              ⁢                                                          ⁢              apparatus                        )                    ⁢                      /                    ⁢                      (                          bandwidth              ⁢                                                                                ⁢                                                                              ⁢              of              ⁢                                                                                ⁢                                                                              ⁢              one              ⁢                                                          ⁢              client              ⁢                                                          ⁢              signal                        )                                              (        1        )            
However, an optical transponder card (i.e., TRPN in FIG. 2) 10-1 through 10-N of a WDM apparatus, which had conventionally provided only a transponder function of an optical signal, has been integrally equipped with ADM functions 11-1 through 11-N of the SONET/SDH signal in the recent years as shown in FIG. 2 (i.e., TRPN 12-1 through 12-N). Owing to this, it is possible to build up a SONET/SDH ring network (i.e., a synchronous digital signal network) in addition to a WDM network just by the WDM apparatuses.
A patent document 1 is available as a conventional technique focusing on the most optimal distribution, noting a method for searching the most optimal portfolio with a high probability of acquiring a high profit. A patent document 2 is available as a conventional technique focusing on allocating shared resources, noting a technique for making an apparatus requiring a use of a shared resource bid an amount of required resources and price, and allocating a resource by processing the bid.
[Patent document 1] Japanese Patent Application Publication No. 2000-293569
[Patent document 2] Japanese Patent Application Publication No. 2003-520496
FIG. 2 shows the difference between the configurations of networks, which is constituted by a SONET/SDH ADM apparatus and a WDM apparatus, and that of an optical network which uses an optical transponder card comprising an ADM on λ function and constituted by the WDM apparatus only. Here, when accommodating a client signal by using the optical transponder card, what is different from the case of using the SONET/SDH ADM apparatus is that the number of client signal ports of the optical transponder cards 12-1 through 12-N is small, that is, at most 10 or thereabouts. This results in two client signals existing:(signal bandwidth of an optical signal of an optical transponder card)/(the number of client signal insertion ports of an optical transponder card)<(bandwidth of a client signal)   (2)(signal bandwidth of an optical signal of an optical transponder card)/(the number of client signal insertion ports of an optical transponder card)≦(bandwidth of a client signal)   (3)
FIGS. 3A through 3C exemplify the case of an accommodation result of a client signal being different between a configuration using the SONET/SDH ADM apparatus and WDM apparatus, and the one using the WDM apparatus equipped with the optical transponder card.
The configurations shown in FIGS. 3A through 3C accommodate each signal (4, 4 and 8) of (2.5 G, 1.25 G and 622 Mbps) in 10 Gbps bandwidth per one wavelength. The number of client ports of the optical transponder card is configured as eight (“8”).
Here,(bandwidth of an optical signal)/(the number of client signal insertion ports)=1.25 Gbps,allowing a client signal meeting both the above noted expressions (2) and (3) to coexist. A design using the conventional SONET/SDH ADM apparatus just maximize a usage ratio of a total band, and therefore accommodates a signal in the order of having a larger band, resulting in generating two optical signals. If it is likewise accommodated by the optical transponder card by considering only the band usage ratio, however, three optical transponder cards are necessary as shown in FIG. 3B, negating an accomplishment of an optimum accommodation by two cards shown in FIG. 3C. This is because the conventional system does not consider a limit in the number of client side ports of an optical transponder card.